The present invention relates to an electronic semiconductor module.
Semiconductor modules of this kind have an insulated metal substrate (IMS) as the carrier substrate; this includes a metal plate which functions as a cooling body and has an electrically insulating layer on its upper side and a thin metal layer arranged on the insulating layer. The insulating layer conducts heat effectively and includes, for example, a thin polymer layer into which ceramic powder is introduced to improve its ability to dissipate heat. Printed conductors are formed on the upper side of the substrate by structuring the metal layer. Electronic semiconductor components are provided on the upper side and electrically connected to the printed conductors via bonding wires. The advantage of using an insulated metal substrate is, in particular, that the heat generated by the semiconductor component can be dissipated effectively into the metal cooling body via the relatively thin insulating layer, which conducts heat effectively.
Aside from insulated metal substrates, the use of direct copper bonded (DCB) substrates in electronic semiconductor modules is known, for example from: H. de Lambilly, H. Keser: Failure Analysis of Power Modules: A Look at the Packaging and Reliability of Large IGBTs, IEEE/CHMT Int. Electronics Manufacturing Technology Symposium 1992, page 366. The direct copper bonded substrates include a relatively thick ceramic carrier, with its upper and lower side being provided with a thin metal layer via a special compression process. Printed conductors are provided on the upper metal layer via structuring. On the upper side of the module, semiconductor components are connected to the printed conductors via bonding wires. A thick metal plate which functions as a heat sink is soldered onto the lower metal layer of the carrier substrate. Furthermore, it is known from European Published Patent Application No. 0 508 717 that cooling channels through which a cooling medium flows can be provided in the metal plate. A particular disadvantage of the direct copper bonded substrates compared with the insulated metal substrates is that the ceramic layer is thick, which makes it more difficult for heat to be transmitted to the cooling body.
The known semiconductor modules described above have the following disadvantage that all the terminal connectors of the semiconductor components are arranged on the upper side of the carrier substrate. Because the printed conductors paths are all in this one position, they are very complicated. In electronic circuits with a high level of integration, the substrate, which is in any case expensive, must be enlarged laterally to house all the necessary printed conductor wiring on the upper side of the carrier substrate. This considerably increases manufacturing costs. It is particularly disadvantageous that because all the terminal connectors are arranged in the upper metal layer of the substrate, significant parasitic inductivity arises and can cause substantial overvoltages. This has a particularly disadvantageous impact if power electronic circuits having direct voltage circuits are arranged on the carrier substrate. The parasitic inductivity causes undesirable overvoltages which have to be taken into account when selecting the semiconductor components. Thus, for example, the switch-off procedure of an electronic circuit breaker has to be slowed via suitable measures so as to reduce overvoltages and prevent damage to the semiconductor module.
The known problems can be avoided via the semiconductor module according to the present invention. It is advantageous that the heat generated by the semiconductor components can be dissipated effectively, and at the same time the parasitic inductivity of the semiconductor module can be significantly reduced. An insulated metal substrate is used as the carrier substrate of the semiconductor module, the insulating intermediate layer of the insulated metal substrate having at least one notch, and at least one terminal face of a semiconductor component provided on the upper side of the semiconductor component facing away from the carrier substrate being electrically connected to a contact element which is directly connected to the metal cooling body via the notch. Because the cooling body is used as an electrical conductor that is directly electrically connected to the terminal of a semiconductor component via the contact element, it is possible to significantly reduce the parasitic inductivity of the semiconductor module. In addition, it is easy to wire the printed conductors, as the metal cooling body also functions as a conductor for conveying the power required to operate the semiconductor component. Thanks to the very thin electrically insulating layer, and respectively, the very thin dielectric between the cooling body and the printed conductors on the upper side of the substrate, the parasitic inductivity is reduced further, and at the same time heat is dissipated into the cooling body very quickly and efficiently.
Advantageously, the contact element can be manufactured as a bonding wire which at one end is connected to the terminal of the semiconductor component and at the other end to the metal cooling body. Bonding wire technology is well understood and thanks to the direct connection between the bonding wire and the cooling body it is only necessary to create small notches in the insulating intermediate layer; these can be created inexpensively using a laser.
Advantageously, the metal cooling body is provided as a potential surface for making available the supply potential, in particular the ground potential, required to operate the semiconductor component.
To ensure that heat is dissipated as effectively as possible and that parasitic inductivity is reduced effectively, it is advantageous if the insulating layer is less than 250 xcexcm thick.
Heat can be dissipated particularly efficiently if the metal cooling body is coupled with a cooling medium. It is particularly advantageous if the metal cooling body of the insulated metal substrate has cooling channels through which the cooling medium flows.
In direct voltage intermediate circuits having an intermediate circuit capacitor it is advantageous if the positive terminal of the capacitor is connected to a printed conductor of the metal layer on the upper side of the substrate and the negative terminal is connected directly to the metal cooling body. This allows the parasitic inductivity to be reduced further.